function sha1(strings) {
	/*
	 *
	 * A JavaScript implementation of the Secure Hash Algorithm, SHA-1, as defined
	 * in FIPS PUB 180-1
	 *
	 * By lizq
	 *
	 * 2006-11-11
	 *
	 */
	/*
	 *
	 * Configurable variables.
	 *
	 */
	var hexcase = 0; /* hex output format. 0 - lowercase; 1 - uppercase */
	var chrsz = 8; /* bits per input character. 8 - ASCII; 16 - Unicode */
	/*
	 *
	 * The main function to calculate message digest
	 *
	 */
	function hex_sha1(s){
	 	//调用该函数返回加密字符
	    return binb2hex(core_sha1(AlignSHA1(s)));
	     
	}
	 
	/*
	 *
	 * Perform a simple self-test to see if the VM is working
	 *
	 */
	function sha1_vm_test(){
	 
	    return hex_sha1("abc") == "a9993e364706816aba3e25717850c26c9cd0d89d";
	     
	}
	 
	/*
	 *
	 * Calculate the SHA-1 of an array of big-endian words, and a bit length
	 *
	 */
	function core_sha1(blockArray){
	 
	    var x = blockArray; // append padding
	    var w = Array(80);
	     
	    var a = 1732584193;
	     
	    var b = -271733879;
	     
	    var c = -1732584194;
	     
	    var d = 271733878;
	     
	    var e = -1009589776;
	     
	    for (var i = 0; i < x.length; i += 16) // 每次处理512位 16*32
	    {
	     
	        var olda = a;
	         
	        var oldb = b;
	         
	        var oldc = c;
	         
	        var oldd = d;
	         
	        var olde = e;
	         
	        for (var j = 0; j < 80; j++) // 对每个512位进行80步操作
	        {
	         
	            if (j < 16) 
	                w[j] = x[i + j];
	             
	            else
	                w[j] = rol(w[j - 3] ^ w[j - 8] ^ w[j - 14] ^ w[j - 16], 1);
	             
	            var t = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)), safe_add(safe_add(e, w[j]), sha1_kt(j)));
	             
	            e = d;
	             
	            d = c;
	             
	            c = rol(b, 30);
	             
	            b = a;
	             
	            a = t;
	             
	        }
	         
	        a = safe_add(a, olda);
	         
	        b = safe_add(b, oldb);
	         
	        c = safe_add(c, oldc);
	         
	        d = safe_add(d, oldd);
	         
	        e = safe_add(e, olde);
	         
	    }
	     
	    return new Array(a, b, c, d, e);
	     
	}
	 
	/*
	 *
	 * Perform the appropriate triplet combination function for the current
	 * iteration
	 *
	 * 返回对应F函数的值
	 *
	 */
	function sha1_ft(t, b, c, d){
	 
	    if (t < 20) 
	        return (b & c) | ((~ b) & d);
	     
	    if (t < 40) 
	        return b ^ c ^ d;
	     
	    if (t < 60) 
	        return (b & c) | (b & d) | (c & d);
	     
	    return b ^ c ^ d; // t<80
	}
	 
	/*
	 *
	 * Determine the appropriate additive constant for the current iteration
	 *
	 * 返回对应的Kt值
	 *
	 */
	function sha1_kt(t){
	 
	    return (t < 20) ? 1518500249 : (t < 40) ? 1859775393 : (t < 60) ? -1894007588 : -899497514;
	     
	}
	 
	/*
	 *
	 * Add integers, wrapping at 2^32. This uses 16-bit operations internally
	 *
	 * to work around bugs in some JS interpreters.
	 *
	 * 将32位数拆成高16位和低16位分别进行相加，从而实现 MOD 2^32 的加法
	 *
	 */
	function safe_add(x, y){
	 
	    var lsw = (x & 0xFFFF) + (y & 0xFFFF);
	     
	    var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
	     
	    return (msw << 16) | (lsw & 0xFFFF);
	     
	}
	 
	/*
	 *
	 * Bitwise rotate a 32-bit number to the left.
	 *
	 * 32位二进制数循环左移
	 *
	 */
	function rol(num, cnt){
	 
	    return (num << cnt) | (num >>> (32 - cnt));
	     
	}
	 
	/*
	 *
	 * The standard SHA1 needs the input string to fit into a block
	 *
	 * This function align the input string to meet the requirement
	 *
	 */
	function AlignSHA1(str){
	 
	    var nblk = ((str.length + 8) >> 6) + 1, blks = new Array(nblk * 16);
	     
	    for (var i = 0; i < nblk * 16; i++) 
	        blks[i] = 0;
	     
	    for (i = 0; i < str.length; i++) 
	     
	        blks[i >> 2] |= str.charCodeAt(i) << (24 - (i & 3) * 8);
	     
	    blks[i >> 2] |= 0x80 << (24 - (i & 3) * 8);
	     
	    blks[nblk * 16 - 1] = str.length * 8;
	     
	    return blks;
	     
	}
	 
	/*
	 *
	 * Convert an array of big-endian words to a hex string.
	 *
	 */
	function binb2hex(binarray){
	 
	    var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
	     
	    var str = "";
	     
	    for (var i = 0; i < binarray.length * 4; i++) {
	     
	        str += hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) * 8 + 4)) & 0xF) +
	         
	        hex_tab.charAt((binarray[i >> 2] >> ((3 - i % 4) * 8)) & 0xF);
	         
	    }
	     
	    return str;
	     
	}
	 
	/*
	 *
	 * calculate MessageDigest accord to source message that inputted
	 *
	 */
	function calcDigest(){
	 
	    var digestM = hex_sha1(document.SHAForm.SourceMessage.value);
	     
	    document.SHAForm.MessageDigest.value = digestM;
	     
	}
	if (!strings) {
		return false;
	}
	return hex_sha1(strings);
}